Electrohydrodynamic (EHD) drying of ginger slices: Impact on drying kinetics, energy efficiency, and phytochemicals retention

Abstract

Conventional thermal drying of ginger often causes losses of heat-sensitive phytochemicals and high energy demand. Electrohydrodynamic (EHD) drying is a promising non-thermal alternative, but the combined effects of operating parameters on drying kinetics, energy efficiency, and quality retention have not been systematically optimized. This study used response surface methodology (RSM) and an artificial neural network integrated with a multi-objective genetic algorithm (ANN-MOGA) to optimize pin-to-plate EHD drying of sliced ginger. Pin spacing (3-5 cm), applied voltage (30-40 kV) and slice thickness (2-4 mm) were varied in a Box-Behnken design, and moisture ratio, drying rate, energy consumption, specific energy consumption, total phenolic content and total flavonoid content were evaluated along with gingerol and 6-gingerol contents determined by LC-MS. Both RSM and ANN models well described the experimental data, with ANN providing higher coefficients of determination. RSM predicted optimal conditions at 5 cm, 34.5 kV and 2 mm, whereas ANN-MOGA yielded 4 cm, 35 kV and 2 mm; both optima combined high drying rate with low specific energy consumption (5.22-6.47 kJ g -1 moisture removed) and high phenolic and flavonoid retention (9.63–9.80 mg GAE g -1 and 5.62-5.86 mg QE g -1 , respectively). Compared with vacuum freeze-drying, EHD-dried ginger at optimized conditions retained higher gingerol and 6-gingerol contents. These results demonstrate pin-to-plate EHD drying as an energy-efficient technology for producing phytochemical-rich dried ginger and highlight ANN-MOGA as a powerful tool for the design and scale-up of EHD and other non-thermal dryers for medicinal plant materials. • Optimization of ginger EHD drying parameters conducted via RSM and ANN-MOGA. • ANN-MOGA demonstrated superior predictive accuracy for optimizing EHD drying. • EHD-dried ginger retained higher gingerol than vacuum freeze-dried samples.